Based on this product's specifications, here are some alternatives and similar models
Flat duct reducer AWENTA KP75-29 75×150 to 55×110 mm
Summary description:
Flat duct reducer AWENTA KP75-29 adapts rectangular ventilation ducts from 75×150 mm to 55×110 mm. Designed for ventilation and air-conditioning installations, it provides a reliable transition between different duct sizes to maintain airflow continuity. Suitable for retrofits or new builds where space or layout requires resizing of flat ducts.